import numpy as np
import pandas as pd

arr = np.arange(12).reshape(3, 4)
df_obj = pd.DataFrame(arr, index=['row_1','row_2','row_3'],
                      columns=['col_1', 'col_2', 'col_3', 'col_4'])
result = df_obj['col_2']
# print(result
# print(df_obj[['col_1', 'col_3']])
print(df_obj[1:3])